damage in electronic equipment

[killabyte]

i work in proffesional audio. i was working with some auto amplified speakers, that means that the amplifier is inside the speaker instead using an additional one to power them.

two guys from electrical company, came to check something and i turned down the main gain in the console, so no signal was available in the amplifier entry. but equipment was still powered. no surge protection was available.

Those guys fixed something there and ready, then moved up and down (quickly) 3 or 4 times the AC breaker mains switch and there was the burned out amplifiers. One IC in two of the cabinets (the same both) literally evaporated the V+ and V- pins, the IC was the high frequency amplifier, both hi freq drivers was burned out too.

how did the transient got in to the amp and evaporated those pins?

thanks for any help.

killa

 

[rodar]

Many power supply sections of equipment don't like
that kind of treatment. They get confused as to
whether in shut down mode or startup if the power is
blinking. Ideally the power supply should shut down
and not try to restart until a time delay and make sure
it is in a stable condition. But that would cost more
components and design time. So in this case I think it
could be an internal amp problem.

Also possible that transients from large inductive
equipment on the same circuit can cause this if disconnected from the source suddenly with no place for
stored inductive energy to go.

Rodar

 

[killabyte]

although inductance of speakers is relatively slow but enegy in capacitors around 20000 microfarads, could a transient supressor have done something against that?

thanks

killa

 

[buzzp]

It certainly could of protected your system from the transients occurring from the rapid energizing and de-energizing of the breaker. Any properly designed electronic device would/should have protection built in for most transients.
As mentioned, its hard to say if transients destroyed the IC or if the thing got confused and did not know what it was doing. There is certainly power available internally to do that kind of damage by way of the large caps.

 

[WoodrowJWeen]

Possibly it was not a transient but instead the neutral wire worked loose intermittently and allowed 208V to reach the electronic equipment instead of 120V. We had this happen in our own office when we first moved in and it fried a "surge supressor" type power strip and a desk lamp but luckily no computers.

 

[jbartos]

Suggestion: More accurate information what was happening might be available via a simulation of equivalent circuits involved and damaged.
The capacitor has a high current inrush on turn on
The inductor has a high voltage spike on turn on
The capacitor has a high voltage spike on turn off
The inductor has a high current on turn off

 

[killabyte]

Tnx to all of you guys i really appreciate your help, in general there´s no general use of protective devices in pro-audio ´cause the high currents and legal spikes of about +6 and even +12dB. Anyway i´ll design a convenient surge suppression scheme for my equipment. case closed

regards
killa